Recent advances in the development of semiconductor and organic light-emitting diodes (LEDs and OLEDs) have made these solid-state devices suitable for use in general illumination applications, including architectural, entertainment, and roadway lighting, for example. Due to their ruggedness, low power requirements, and long life, these devices are becoming increasingly competitive with light sources such as incandescent, fluorescent, and high-intensity discharge lamps.
Early methods of packaging the semiconductor LED die include a lead frame that holds the chip and extends to provide an electrical connection. The chip can then be encapsulated in an epoxy plastic package that may be coloured or shaped. Later LED packagings are tailored for surface mounting the LEDs onto a printed circuit board (PCB) such as disclosed in U.S. Pat. No. 4,781,960, where the LED is mounted in an insulating housing secured by a pair of legs with relatively broad feet which are soldered to conductive pads on the surface of a PCB. The leads of the LED are spot welded to the legs to make electrical connections between the LED and the circuit board.
Electronic devices such as LEDs, however are susceptible to moisture which can interact with the LED die materials and can destroy or cause malfunction of the devices.
U.S. Pat. No. 5,722,767 provides a means to protect a LED system from exposure to moisture. The LED display panel structure comprises a PCB, a front plate having a plurality of through-holes defined therein, a plurality of washers, each of which is provided on a back surface of the front plate in correspondence with each of the through-holes, a plurality of LEDs, each of which is inserted through a central aperture and each of the washers being smaller than a diameter of the LED to be clamped therein. There is also a plurality of holders, each of which has a first recess and a second recess, such that each of the holders receives and holds each of the LEDs in its first recess and is attached on the PCB by water resistant adhesive filled in the second recess. A pair of through-bores between the first recess with the second recess receives a pair of leads which connect each LED to the PCB. In this manner, the circuitry of the LEDs and PCB are protected from moisture. This design, however is specific to a particular and outdated LED packaging and may not be as effective for use with contemporary LEDs and their associated packaging.
In addition, U.S. Pat. Nos. 5,927,845, 5,848,837 and 6,673,292 all define various forms of an integral single piece extruded LED light strip and an associated process for producing such an LED light strip. The light strip includes first and second bus elements spaced apart from one another by a predetermined distance. The light strip also includes at least one LED connected between the first and second bus elements and is illuminated when the first bus element conducts electricity provided from a power source. An extruded plastic material completely encapsulates the first and second bus elements and the LED, and provides a barrier that protects the elements from damage and makes the light strip impermeable to moisture. This solution, however is more specific to linear LED strips and as such is not suitable for planar LED configurations.
Therefore, with LEDs becoming increasingly competitive with other light sources for use outdoors and in environments with high moisture contents, there is an apparent need for a method and apparatus for protecting these devices from moisture that is cost effective and easy to perform and not limited to a more linear arrangement of LEDs.
This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.